Western Digital Technologies, Inc.

Shafa Dahandeh

Kent Douglas Anderson

Anantha Raman Krishnan

Guangming Lu

Alvin Jianjiang Wang

Shayan Srinivasa Garani

David W Wheelock

Andrew John Tomlin

Ming Jin

Noureddine Kermiche

Galvin Chia

Alvin W Tan

Aravind Raghunathan

An error management system for a data storage device can generate soft-decision log-likelihood ratios (LLRs) using multiple reads of memory locations. Bit patterns provided by multiple reads of reference memory locations can be counted and used to generate probability data that is used to generate possible LLR values for decoding target pages. Possible LLR values are stored in one or more look-up tables.

Method and system for decoding data based on association of first memory location and second memory location

Soft-decision input generation for data storage systems

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A first data track is read to generate a first read signal, the first read signal is sampled to generate first read signal samples, a first data sequence is detected based on the first read signal samples, and the first data sequence is converted into corresponding first expected samples. A second data track adjacent the first data track is read to generate a second read signal, the second read signal is sampled to generate second read signal samples, and a second data sequence is detected based on the second read signal samples and the first expected samples.

Data storage device comprising sequence detector compensating for inter-track interference

A reader failover system and method are described for a data storage system. At least two reader systems, including a first reader element and a second reader element, situated on the same head, are employed to read a magnetic storage medium. In an aspect, the head is a two-dimensional magnetic recording (TDMR) head. Control circuitry detects when the first reader system provides less than a predetermined performance or fails, and thereafter causes the second reader system, but not the first reader system, to read the magnetic storage medium. In an aspect, a buffer stores a first reader element signal until the control circuitry detects whether or not the first reader element provides less than a predetermined performance or fails. In an aspect, when a reader element fails, data recovery is performed, and all of, or a majority of, the media continues to be readable, improving the data storage system robustness.

Read failover method and apparatus for a data storage system

A waterfall manufacturing process and apparatus are described for a data storage device. In an aspect, a determination is made during manufacturing of a magnetic storage medium reader system whether a first reader system provides less than a predetermined performance or is nonfunctioning. The reader system includes at least the first reader system and a second reader system with reader elements on the same head. When the first reader system is determined to provide less than the predetermined performance or is nonfunctioning, the reader system is reconfigured during the manufacturing to utilize the second reader system, but not utilize the first reader system, to read the magnetic storage medium. Alternatively, the reader system is reconfigured during manufacturing to read the magnetic storage medium at less than the predetermined performance, or the reader system is situated with a different data storage device configured to function with less than the predetermined performance.

Waterfall method and apparatus for a data storage device read system

A disk drive is disclosed comprising a disk comprising a plurality of data tracks, and a head comprising a first read element and a second read element. The first read element is positioned over a first data track and the second read element is positioned over a second data track. A first analog read signal emanating from the first read element is adjusted based on a second analog read signal emanating from the second read element in order to reduce noise in the first analog read signal due to interference from the second data track.

Disk drive compensating for inter-track interference in analog read signal

A data storage system configured to adaptively code data and related methods are disclosed. In some embodiments of the present invention, a data storage system includes a controller and a non-volatile memory array having a plurality of memory pages. The controller includes a channel monitor that determines the quality of read signals from the pages when they are read, and provides adjustment metrics to aid in the selection of a code rate, such as a code rate for a low-density parity-check (LDPC) code. In this way, the code rate used for data encoding can be dynamically adjusted to accommodate degradation of the non-volatile memory array over its useable life.

Method and system for monitoring data channel to enable use of dynamically adjustable LDPC coding parameters in a data storage system

A data storage device is disclosed comprising a disk comprising a plurality of data tracks, and a head comprising a first read element and a second read element. A first data track is read using the first read element to generate a first read signal, and the first read signal is sampled to generate first signal samples. A first branch metric is generated in a first trellis sequence detector when detecting a first data sequence based on one of the first signal samples. A second data track adjacent the first data track is read using the second read element to generate a second read signal, and the second read signal is sampled to generate second signal samples. A second branch metric is generated in a second trellis sequence detector when detecting a second data sequence based on one of the second signal samples and the first branch metric.

Data storage device using branch metric from adjacent track to compensate for inter-track interference

A data storage device is disclosed comprising a non-volatile memory (NVM). First data is written to a first area of the NVM, and a first estimated data sequence is read from the first area of the NVM. The first estimated data sequence is first decoded, and a log-likelihood ratio (LLR) is first updated based on the first decode. Second data is written to a second area of the NVM, and a second estimated data sequence is read from the second area of the non-volatile memory. The second estimated data sequence is second decoded in response to the first updated LLR, and the LLR is second updated based on the second decode.

Data storage device tracking log-likelihood ratio for a decoder based on past performance

A disk drive is disclosed comprising a head actuated over a disk and a fly height actuator operable to control a fly height of the head in response to a fly height control signal. A touchdown operation is executed to set an operating fly height control signal by adjusting the fly height control signal until the head contacts the disk. A fly height calibration track is then read to set a fly height reference. When calibrating the operating fly height control signal, the fly height calibration track is read and the operating fly height control signal is adjusted in response to the fly height reference. When the adjusted operating fly height control signal is invalid, the touchdown operation is re-executed to reset the operating fly height control signal and then the fly height calibration track is read to reset the fly height reference.

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Laguna Niguel, CA, United States of America

Shafa Dahandeh